[PATCH 5.10 131/406] drm/amdgpu: avoid integer overflow warning in amdgpu_device_resize_fb_bar()

Greg Kroah-Hartman
2023-09-17T19:25:46Z

From: Arnd Bergmann <arnd@arndb.de>

[ Upstream commit 822130b5e8834ab30ad410cf19a582e5014b9a85 ]

On 32-bit architectures comparing a resource against a value larger than
U32_MAX can cause a warning:

drivers/gpu/drm/amd/amdgpu/amdgpu_device.c:1344:18: error: result of comparison of constant 4294967296 with expression of type 'resource_size_t' (aka 'unsigned int') is always false [-Werror,-Wtautological-constant-out-of-range-compare]
res->start > 0x100000000ull)
~~~~~~~~~~ ^ ~~~~~~~~~~~~~~

As gcc does not warn about this in dead code, add an IS_ENABLED() check at
the start of the function. This will always return success but not actually resize
the BAR on 32-bit architectures without high memory, which is exactly what
we want here, as the driver can fall back to bank switching the VRAM
access.

Fixes: 31b8adab3247 ("drm/amdgpu: require a root bus window above 4GB for BAR resize")
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
index 8bd887fb6e631..f0db9724ca85e 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
@@ -1091,6 +1091,9 @@ int amdgpu_device_resize_fb_bar(struct amdgpu_device *adev)
u16 cmd;
int r;

+ if (!IS_ENABLED(CONFIG_PHYS_ADDR_T_64BIT))
+ return 0;
+
/* Bypass for VF */
if (amdgpu_sriov_vf(adev))
return 0;
--
2.40.1